1. Field of the Invention
The invention relates to optical burst mode reception, and in particular to an optical burst mode receiver not affected by noise when no optical signal is received.
2. Description of the Related Art
Optical burst mode receivers receive optical signals from a plurality of optical communication network devices connected in parallel. Because of the discrete transmission distances data breaks occur. The optical receiver is incapable of determining duration of breaks. Data with such breaks are referred to as burst mode. Differing intensities and qualities of the received optical signals require a technique that can identify the data received by optical burst mode receivers.
FIG. 1 shows a conventional burst mode receiver that comprises an optical photo-detector 11, a transimpedance amplifier 12, and a limiting amplifier 13. The photo-detector 11 is operative to receive an optical signal L1 and convert the received optical signal to a current signal S1. The intensity of the optical signal L1 affects the value of the current signal S1. The transimpedance amplifier 12 is operative to receive the current signal S1 and to convert the current signal S1 to a first transmit signal S2 and a second transmit signal S3. The current signal S1 is amplified and shifted to generate the first transmit signal S2. The first transmit signal S2 and the second transmit signal S3 are symmetric with respect to a DC current. The limiting amplifier 13 is operative to receive the first transmit signal S2 and the second transmit signal S3 to generate a digital data signal S4.
The limiting amplifier 13 amplifies burst mode signals received by the optical burst mode receiver. However, limiting amplifier 13 oscillates, generating noise, even though no optical signal is received. The long-term oscillation degrades the limiting amplifier 13. Some available solutions attempt to integrate or feed feedback to the single input terminal or both input terminals of the limiting amplifier 13. Hence, when no optical signal is received, the input terminals of the limiting amplifier 13 are at different voltage levels, preventing oscillation caused by noise. However, the above-mentioned solutions increase the time consumption and affect data quality, with attendant unreliable data determination.